1. Field of the Invention
The present invention relates to the field of Urology.
2. Prior Art
Ureteral stents to provide drainage from the kidneys to the bladder are placed in position in the ureter through an appropriate scope system, typically in retrograde fashion through a cystoscope having a working channel large enough to put the required instruments through, such as stents, guide wires, forceps and the like. Placement of such a large scope into a patient's urethra requires anesthesia and a "cysto-room" environment.
After the scope is placed through the urethra and the tip is within the bladder, the stent is then advanced through the scope, through the bladder and into the ureter. At the point where the stent or part of the stent is in the ureter, the tip of the stent and its full location is no longer visible directly by means of the scope, the scope being too large to itself also be advanced into the ureter. Thus the stent and guide wire must be positioned and progress must be viewed by means of fluoroscopy or ultrasound from outside the patient. Manipulation of the stent and cystoscope while trying to interpret the image given by either fluoroscopy or ultrasound can become quite difficult. In any event, after the stent is in the desired location as detected by a combination of direct vision and fluoroscopy or ultrasound, the stent is left in place by some means of pushing the stent off of its working guide wire or stylet, after which the guide wire or stylet is removed, followed by the removal of the scope from the urethra.
This procedure, though quite routine, is quite cumbersome, as the doctor operating the cystoscope must be sitting low between the patient's legs, and must bend over to view through the cystoscope. Since direct vision is lost anywhere past the bladder, it is not possible for the doctor to actually see where the stent is going, what the condition of the ureter is, what potential obstructions look like, or if a kidney stone is embedded within the walls of the ureter. Thus upon encountering an obstruction, the doctor's options are highly limited, the most obvious option merely being to try to negotiate past the obstruction and proceed with the placement of the stent irrespective of the nature of the obstruction, presence of a kidney stone, etc. For this purpose various forms of stents and guide wires are known.
One form of stent and guide wire system is shown in U.S. Pat. No. 4,307,723. As shown therein, the stent is an elongated, flexible, generally cylindrical member having the proximal end of the stent closed and set in the form of a hook, with the other end also set in the form of a hook with a longitudinal intermediate portion connecting the hooked ends. A stylet is inserted through the open end of the stent and passed through substantially the full length of the stent to straighten both hooks. Also, a stent pusher is threaded over the wire stylet and inserted into the open end of the stent a certain amount to allow the partial withdrawal and redirection of the stent if necessary during the retrograde cystoscope insertion process hereinbefore described. Once the stent is properly positioned, the stylet and stent pusher are removed by withdrawing the stent pusher while holding the wire stylet, causing the stent and stent pusher to disengage, after which the wire stylet and then the stent pusher are withdrawn.
Other stents are of somewhat similar construction to the foregoing though open at the proximal end, with a stent pusher being used to push against the distal end of the stent to encourage the same to move together with (or after) the guide wire into position, after which the stent pusher is used to retain the stent in position as the guide wire is withdrawn, with the stent pusher itself then being withdrawn.
In U.S. Pat. No. 4,610,657, a ureteral stent is disclosed having both ends thereof open, but with the opening at the proximal end being smaller than the opening of the lumen and distal end. In this way, a small guide wire may be inserted through the lumen and through the proximal end to negotiate past obstructions, etc., or alternatively a larger guide wire could be inserted to pass through the lumen, but not through the smaller opening in the proximal end, to act as a stent pusher for stent insertion purposes.
In addition to the foregoing, two-piece guide wires are also known. Such guide wires generally comprise a helically wound flexible outer guide wire portion typically closed at the proximal end, and a solid, more rigid inner guide wire removably positioned within the flexible outer guide wire portion. In this manner, the two guide wire members together may be used as a single guide wire and if necessary, the more rigid central guide wire may be partially withdrawn, making the proximal end of the outer guide wire member more flexible to better manipulate the same past obstructions (See, for instance, U.S. Pat. No. 4,713,049 for a dual guide wire system of this general type).
Obviously, from the foregoing description, cystoscopes for passing through the urethra and into the bladder and having an auxiliary port for insertion of the stent, guide wire, pusher, etc. are well known. In general the auxiliary port of such devices is located to the side of the fiber optic scope, which scope is normally as large as or larger than the stent itself. Thus the overall combination of the fiber optic bundle, cystoscope body, stent, stent pusher, guide wire, etc. is relatively large, requiring that the patient be anesthetized as mentioned before, and being much too large for passage beyond the bladder into the ureter. See for instance, U.S. Pat. No. 4,738,659 disclosing a catheter for use with a cystoscopic lens. Also, of course, such fiber optic scopes are themselves well known in the prior art, such as by way of example as disclosed in U.S. Pat. No. 3,417,745.